3.0 Stream Assessment

Transcription

1 3.0 Stream Assessment 3.1 Methods Stream aquatic integrity in urban settings is directly affected by the physical changes in the watershed, some of which result in the degradation of the chemical and/or physical conditions of the stream. Habitat, morphological, and infrastructure conditions (pipe crossing, road crossings, discharges, etc.) are extremely important for discriminating between physical and chemical effects. A holistic approach integrating habitat and riparian zone information with an evaluation of problem areas and general infrastructure data provides a comprehensive stream assessment. This approach provides a means to assess the impacts of watershed changes and storm water infrastructure on the riparian corridor and stream integrity. County and CH2M HILL staff have worked together to develop a quality set of assessment protocols that will provide the information necessary for effective implementation of the watershed management program while streamlining the process to ensure efficient assessments. The protocols for evaluating potential for biological inhabitation of the streams included a habitat assessment based on the GAEPD (2000) Draft Standard Operating Procedures-Freshwater Macroinvertebrate Biological Assessment protocols and EPA Rapid Bioassessment Protocols (Barbour et al., 1999). Protocols and field forms were prepared for documenting severe bank erosion, impaired buffers, and problems causing stream degradation associated with infrastructure and other issues. CH2M HILL used similar protocols on several other projects in the local area (Clayton County, CH2M HILL, 2000; Hartsfield Atlanta International Airport, CH2M HILL, 2000) evaluating over 50 miles of streams and on several projects in the east and southeast evaluating over 1,500 miles of streams in Virginia alone. The Maryland Department of Natural Resources adopted these inventory methods for stream corridor assessment survey to prioritize watershed restoration efforts (Yetman, K, 2002). The stream assessment protocols include instructions to photograph and locate storm water and drainage infrastructure and potential problem areas. Specific instructions were developed to ensure uniformity of the documentation of pipe outfalls, culverts, bridges, dams, and other utility structures. Protocol instructions and procedures contained detailed descriptions of the different elements of the assessments and hints on what to look for in the field. The resulting stream assessment information can be used to identify and prioritize BMPs and watershed management practices that will be most effective in minimizing the effects of watershed development on stream integrity. The stream assessment was performed in two phases. Phase 1 involved a general evaluation including habitat assessments and inventories of infrastructure, problem areas, and stream morphologic characteristics (Appendix A). When an inventory item was identified, it was documented on the appropriate inventory form, with the requested information, and identified on the map, and, if appropriate, a photograph was taken and logged on the inventory form and the photo log. An impact score was assigned to each inventory item according to ATL\P:\162663\FINAL REPORT DOCUMENTS\FINAL\MASTERPLANREPORT_SECT 3.DOC 3-1

2 the criteria listed on the bottom of each inventory form. These data were used to identify the most disturbed stream reaches for the Phase 2 studies to then recommend different levels and types of stream improvement projects Phase 1 Studies The mainstem and tributaries of Crooked Creek were subdivided into reaches or segments depending on habitat condition factors (e.g., flow energy, riparian zone condition and other features) and/or morphological stream type. Thus, the number of study reaches was dependent on field conditions observed during the Phase 1 pedestrian stream survey. Stream segments considered in the Phase 1 study and their locations are shown in Figure 3. During the stream walks, the biologists and engineers recorded the physical habitat and riparian conditions on the field data forms and used photography to document severe conditions (see Appendix A for field forms). Conditions in tributary streams and storm water drainage channels were also evaluated during this process. The following provides an overview for the field studies for conducting inventory, morphological evaluation, and habitat assessment Stream Inventory and Condition Factors The stream inventories include pipes, drainage ditches, utility lines, road crossings, erosion problems, illegal dumping, obstructions, and buffer conditions within the riparian corridor. Impact scores from 0 to 10, with 10 being the worst condition, were assigned to each of the following inventory items, allowing for ranking of individual stream reaches. Stream Characteristics: General water quality conditions, such as color, odor, surface scum, turbidity, etc. Pipe: Location and size of each pipe, type of discharge, discharge quality, erosion downstream of pipe, and condition of pipe. Drainage Ditch: Location of storm water conveyances, erosion, and water quality concerns. Obstructions: Location of major obstructions that present a significant flooding hazard or erosion problem. Dump Sites: Location and condition of any illegal dump sites. Public Utility Lines: Condition and location of utility lines. If a utility line was leaking it was assigned a value of 20 as an alert for immediate attention and the DPU was notified. These data will be compared with County GIS information as supplemental information. Erosion Problems: Location and size of major stream bank erosion areas. Road Crossings: Location of road crossings, primarily the condition of the culverts, sedimentation, and erosion around the culverts. Photographs: Pictures of any problem areas were taken and documented on a photo-log. A CD with photographs was prepared. The photo-log included: Downstream end of reach looking upstream Upstream end of reach looking downstream ATL\P:\162663\FINAL REPORT DOCUMENTS\FINAL\MASTERPLANREPORT_SECT 3.DOC 3-2

3 Each problem area that was entered on the inventory forms. Field maps: Field maps were annotated identifying the location of features documented (see above list). The WPP identified TSS as one of the primary causes of stream habitat degradation. Bank erosion problems were identified as a source of the TSS. The following scoring criteria were established based on the extent of the problem: Extreme Impending threat to structures or infrastructure. Score 10 Severe Area of erosion is damaging property and causing obvious in-stream degradation. Eroding bank is generally 5 feet or greater in height. Score 7 Moderate -- Area of erosion may be damaging property and causing some in-stream degradation. Eroding bank is generally 2 to 3 feet or greater in height. Score 5 Minor Area of erosion is a low threat to property, no noticeable in-stream degradation. NA The length of the eroded bank was recorded for calculation of total area of eroded bank Morphological Evaluation of Stream Types The following quantitative and qualitative data were collected to conduct a morphologic evaluation: Stream width at bankfull (determined by field indicators), Bankfull depth (deepest spot in the stream) Floodprone stage (Twice the bankfull depth). Examples of these morphological features are shown in Figure 4. The stream characteristics quantified were used to develop a Rosgen stream classification for use in understanding and predicting fundamental qualities about the types of streams in the watershed (see Appendix B for field sheets). Rosgen stream classification includes eight stream types (Rosgen, 1996). The morphology (form and structure) of the stream channel is governed by physical processes that can be documented through observable stream channel features, such as bankfull width and depth and measurements of related stream processes such as stream flow and velocity. According to Leopold et al. (1964) stream channel pattern is directly influenced by the bankfull morphological features dimensions and the flow pattern. Bankfull measurements are probably the most important variables for making a stream type determination. A change in any one of the bankfull morphological features or flow sets up a series of channel adjustments that lead to changes in the other channel features, resulting in channel pattern alteration, which are often accompanied by erosion and other kinds of channel instability. Because stream morphology is the product of this integrative process, the bankfull variables and floodprone stage were qualitatively evaluated during the field reconnaissance. The morphological data were then used to assign to a particular reach one of eight stream types (Rosgen, 1996). Table 2 is a brief description of the Rosgen stream types and ATL\P:\162663\FINAL REPORT DOCUMENTS\FINAL\MASTERPLANREPORT_SECT 3.DOC 3-3

4 assessment criteria used to categorize streams in the Crooked Creek watershed. Assigning a stream type to a reach is an iterative process in which the data for each feature are compared to a set of criteria. TABLE 2 General Stream Type Descriptions and Delineation Criteria for Rosgen Level 1 Classification (stream type) Stream Type General Description Entrenchment Ratio a W/D Ratio b Sinuosity c Slope d A B C D Steep, entrenched, cascading, step/pool streams. High energy debris transport associated with depositional soils. Very stable if bedrock- or boulder-dominated channel. Moderately entrenched, moderate gradient, riffledominated channel, with infrequently spaced pools. Very stable plan and profile. Stable banks. Low gradient, meandering, point-bar, riffle/pool, alluvial channels with broad, well defined floodplains. Braided channel with longitudinal and transverse bars. Very wide channel with eroding banks. <1.4 < to to to 2.2 >12 >1.2 2 to 4 >2.2 >12 >1.2 <2 n/a >40 n/a <4 DA Anastomosing (multiple channels) narrow and deep with extensive, well vegetated floodplains and associated wetlands. Very gentle relief with highly variable sinuosities and width/depth ratios. Very stable stream banks. >2.2 Highly variable Highly variable <0.5 E F G Low gradient meandering riffle/pool stream with low width/depth ratio and little deposition. Very efficient and stable. High meander/width ratio. Entrenched meandering riffle/pool channel on low gradients with high width/depth ratio. Entrenched gully step/pool and low width /depth ratio on moderate gradients. >2.2 <12 >1.5 <2 <1.4 >12 >1.2 <2 <1.4 <12 >1.2 2 to 4 Source: Rosgen, 1996 a The entrenchment ratio measures the degree that the channel is cut and it relative shape. The entrenchment ratio is equal to the floodprone width/bankfull width. b The width to depth ratio is an index value which indicates the shape of he channel cross-section (ratio of bankfull width /mean bankfull depth. c Sinuosity is a measure of the meander of the stream in its valley and is defined as the stream length/valley length. d Slope measures the change in topography of the channel based on the surface of the water. The slope is equal to the vertical distance divided by the horizontal distance. A cursory observation was also made of the dominant particle size found in the channel banks and bed, to make a preliminary determination of Rosgen Level II stream classification. Level II provides more detailed morphological descriptions of channels, with a higher resolution of information and thus greater usefulness in management applications. Figure 5 presents a classification key that includes the use of channel material as a factor to define a stream type. The Level II classification for each stream reach in the Crooked Creek Watershed is shown in Figure 6. ATL\P:\162663\FINAL REPORT DOCUMENTS\FINAL\MASTERPLANREPORT_SECT 3.DOC 3-4

5 For Crooked Creek, the Rosgen stream type classifications were used to make a preliminary determination about restoration activities most likely to succeed in a given stream reach. For example, from Rosgen (1996), a G type stream reacts poorly to log sills, boulder clusters, and deflectors. This stream type is still incising and widening and the hydraulic forces would negate these restoration and stabilizing methods. Boulder toe protection, root wads, and vortex rock weirs, on the other hand, promote stability in G type streams Habitat Assessment The habitat assessment provides a semi-quantitative evaluation of the physical condition of the channel and riparian zone and indicates whether key physical characteristics of the stream and adjacent land uses are adversely affecting the structure of the aquatic community and overall stream integrity. Habitat assessments were conducted using the modified Georgia Draft Standard Operating Procedures-Freshwater Macroinvertebrate Biological Assessment (GAEPD, 2000). The habitat assessment process involves rating each of ten parameters, which vary depending on whether the prevalent stream configuration is riffle/run or glide/pool (Table 3). TABLE 3 Habitat Assessment Parameters for Riffle/Run and Glide/Pool Systems Riffle/Run System Glide/Pool System In-stream Cover (fish) Bottom Substrate/Available Cover Epifaunal Substrates (benthic) Pool Substrate Characterization Embeddedness Pool Variability Channel Alteration Channel Alteration Sediment Deposition Sediment Deposition Frequency of Riffles Channel Sinuosity Channel Flow Status Channel Flow Status Bank Vegetative Protection Bank Vegetative Protection Bank Stability Bank Stability Riparian Vegetative Zone Riparian Vegetative Zone Habitat characteristics such as variety in habitat types, degradation of habitats from erosion and sediment deposition, and human impacts to the stream were rated, providing a habitat score for each unique stream segment. Other observations made include water color, water odor, and aquatic plants (see Appendix C for field sheets used in the habitat assessment). For QA/QC, two team members individually performed the habitat assessment and the total scores were compared. If the total habitat scores deviated by 30 or more points from the other assessors scores, the team members discussed each factor, identifying the rationale for assigning scores, and making appropriate mutually agreed changes. The average of the scores from the two assessors was assigned to each reach. Habitat scores for Crooked Creek stream reaches are shown in Figure 6. ATL\P:\162663\FINAL REPORT DOCUMENTS\FINAL\MASTERPLANREPORT_SECT 3.DOC 3-5

6 Additional Information Stream Reach Nomenclature The following naming convention was used to document the stream infrastructure and condition factors on field forms and to document and identify the location of the observations on field maps: (Stream Code)(Reach ).(Factor Code)(list number) Stream Code is a two-letter abbreviation of the stream name, which identifies the stream or tributary. Reach identifies the portion (or reach) of stream being evaluated. Factor Code identifies the infrastructure or condition observed, and List Number is a counter for the number of occurrences of each infrastructure item or condition. Table 4 presents the stream and factor codes. Figure 6 shows the stream codes and reach numbers for the study area. TABLE 4 Stream and Factor Codes Stream Name Crooked Creek Inventory Item Pipe Ditch (Open Channel) Dump Utility Obstruction Erosion Road Crossing Stream Code CC Factor Code P D M U T E C Example: CC02.D04 is Crooked Creek, Reach 2, 4 th ditch Each inventory item was assigned an impact score ranging from 0 to 10 according to a prescribed definition listed on each inventory form. As indicated earlier, an out-of-range score of 20 was assigned to leaking utility lines to flag them for immediate attention. The impact scores were used in the process of ranking stream reaches. Photo-Log All photographs were recorded on a photo-log, which included a brief description of the picture. The location and direction of photographs were documented on field maps. At a minimum, the following photographs were taken: Downstream end of reach looking upstream Upstream end of reach looking downstream Each problem area that was entered on the inventory forms. A photo-log on CD with a location reference map has been provided to Gwinnett County separate from this report. ATL\P:\162663\FINAL REPORT DOCUMENTS\FINAL\MASTERPLANREPORT_SECT 3.DOC 3-6

7 3.1.2 Phase 2 Studies The second phase of field investigations focused on confirming the initial assessment data, noting site constraints that might affect engineering design, and developing restoration concepts for each stream reach. This information was used in further prioritization of restoration potential and projects in the Crooked Creek basin. 3.2 Results Stream Inventory and Condition Factor Inventory Within the 32 reaches identified and evaluated, the following stream inventory and condition factors affecting the overall aquatic integrity were identified. Note that these observations of existing conditions are not necessarily items that need immediate attention. Critical items, such as potential sewer line leaks, were reported to Gwinnett DPU for further action through the County s service request system. 118 Erosion Problems (see Figure 7) 53 Drainage Ditches (see Figure 8) 20 Pipes (see Figure 9) 13 Obstructions (see Figure 10) 7 Dump Sites (see Figure 11) 16 Public Utility Lines (see Figure 12) 21 Road Crossings (see Figure 13) The results of the detailed data collected for each inventory point are summarized in Appendix D Morphological Stream Types The physical conditions of Crooked Creek watershed streams, based on morphological characteristics, are summarized in Table 5. At least 20 of the stream channels were deeply incised with steep banks, resulting severely entrenched channels. The significant erosion areas were located in G and F streams. TABLE 5 Summary of Physical Conditions in Crooked Creek Watershed Streams Number Stream Type 4 B Moderately entrenched streams with a moderate gradient forming a rifle-dominated channel with infrequently spaced pools. Very stable plan, profile, and banks. 9 E Low gradient meandering glide/pool streams with low width/depth ratio and little deposition. Very efficient at moving sediment and stable with meanders and an active floodplain. 3 F Entrenched meandering riffle/pool complex channel on low gradients with high width/depth ratio. Laterally unstable stream with highly eroding banks. 17 G Entrenched gully step/pool systems with slow width /depth ratio on low to moderate gradients. Highly unstable with eroding banks and grade control problems. Adapted from Rosgen, 1996 ATL\P:\162663\FINAL REPORT DOCUMENTS\FINAL\MASTERPLANREPORT_SECT 3.DOC 3-7

8 3.2.3 Habitat Assessment Approximately 19 miles of stream were evaluated during this study and a total of 32 unique reaches were identified based on habitat characteristics and/or morphology. Of the 32 reaches identified, habitat assessments were conducted at 28. Stream reaches with the highest habitat scores were generally located in headwater areas or where urban development was less concentrated. Table 6 and Figure 6 present the habitat scores, geomorphologic classifications (stream type), and the corresponding study reaches. TABLE 6 Habitat Scores Measured on Stream Reaches in Crooked Creek Watershed Reach Score a Morphological Classification TR G5 CC B1 CC G5 TR G5 TR E6 TR G5 TR E5 89 G5 TR G5 TR G5 TR G5 CC G5 CC F5 TR G5 101 F5 TR G1 TR E5 CC G3 TR G1 TR G5 TR G4 TR B5 120 E5 TR E5 TR B5 TR F5 TR G5 TR E3 TR ND E5 TR ND G5 TR ND E5 TR6-01 ND B1 a A low score indicates low quality habitat condition. ND = No data collected. Stream channels were too small for appropriate assessment. Barbour et al. (1999) recommend condition category assignments corresponding to four primary and three secondary ranges of habitat scores as follows: ATL\P:\162663\FINAL REPORT DOCUMENTS\FINAL\MASTERPLANREPORT_SECT 3.DOC 3-8

9 Score Condition Category 0 to 47 Poor 48 to 50 Poor/Marginal 60 to 100 Marginal 101 to112 Marginal/Sub-optimal 113 to 153 Sub-optimal 154 to 165 Sub-optimal/Optimal 166 to 200 Optimal Approximately half of the stream reaches listed in Table 6 are marginally disturbed and are not likely to support a diverse biological community typical of an undisturbed Piedmont province stream. The physical habitat conditions of the streams and riparian zones of the remaining reaches range from marginal to sub-optimal. Because these streams are also degraded to some extent, the diversity of the biological community they support is diminished as well, although to a lesser degree. In general, the stream channel habitat metrics scored poor to marginal throughout the study area, indicating that the stream reaches evaluated have been degraded to some degree. In some areas, bank erosion was substantial and contributed to the sedimentation and poor conditions in these streams. Furthermore, the epifaunal substrate and in-stream cover, which were buried by sediment, scored especially low. For the most part, the riparian zone along the banks has been cleared of natural vegetation and replaced with turf grasses or impervious surfaces. The channel flow metric indicated that extensive channel widening has occurred, causing the flow to be confined to the thalweg (deepest channel in the streambed), which is only a small portion of the streambed. In streams that have not been eroded or unnaturally widened, the normal flow, and sometimes the normal low flows, flood the stream channel from bank to bank at the toe of slope. 3.3 Stream/Reach Ranking The purpose of this ranking is to categorize the stream segments based on the amount and severity of habitat degradation observed in the field, thereby identifying the stream segments that have experienced the greatest degradation of biotic integrity. The ranking involved reviewing the stream and riparian zone data and then sorting stream reaches by habitat assessment score and inventory scores. The habitat scores, which included 10 metrics (10 points each for each of the two stream banks), were evaluated and were shown in ascending order (i.e., increasing habitat integrity) in Table 6. The metrics on which the habitat scores were rated are shown in Table 3. The results of the detailed data collected for each stream inventory point and calculated scores are presented in Table 7. The raw data used in preparing the reach scores is presented in Appendix D. Relating the habitat scores to the other stream survey scores required the inverse calculation of habitat scores, because habitat scores decrease in value with degradation but the inventory scores increase in value with degradation. This inverse habitat score was calculated by subtracting the measured scores from 200, the maximum possible habitat score. The results of these calculations are shown in Table 7, which lists the stream reaches from worst ATL\P:\162663\FINAL REPORT DOCUMENTS\FINAL\MASTERPLANREPORT_SECT 3.DOC 3-9

10 to best condition. Highest ranked streams (worst) have the greatest potential for improvement in biotic integrity because of existing poor conditions. TABLE 7 List Relating Habitat Assessment and Inventory Factor Scores a to Each Other Rank Reach Habitat Inverse Erosion Open Channels Road Crossing Scores a Public Utilities Pipes Obstructions Total Score 1 TR TR CC CC TR CC CC TR TR CC TR TR TR TR TR TR TR TR TR TR TR TR TR TR TR ND NA 30 TR ND NA 31 TR ND NA 32 TR6-01 ND NA a The inventory and condition factors were evaluated based on the average score for the erosion inventory and total score for all remaining inventory categories. Average scores, rather than total, were used in Table 7 for the erosion inventory because they effectively represented an area measurement (length and height) and severity of stream ATL\P:\162663\FINAL REPORT DOCUMENTS\FINAL\MASTERPLANREPORT_SECT 3.DOC 3-10

11 degradation. The average erosion score was determined by taking the average of the scores used to rate the different erosion observed in each reach. For example, in reach CC-01, 7 substantial erosion areas were observed and each was assigned a score as follows: Erosion Site Erosion Score CC-01.E01 4 CC-01.E02 8 CC-01.E03 8 CC-01.E04 6 CC-01.E05 4 CC-01.E06 5 CC-01.E07 4 The average value for these seven erosion areas is 5.6. The other inventory measurements (pipes, crossings, etc.), which identified point locations of stream degradation, were best represented by total score (see Appendix D for calculations). The inverse habitat, erosion, and other inventory scores were added together and these total scores are listed from highest (worst) to lowest (best) and given a directly corresponding rank; the highest (worst) score is ranked 1, the second highest (worst) score is ranked 2, etc. Generally, the streams with the worst habitat scores were ranked highest. This was partly due to the fact that the habitat assessment considered 10 stream assessment factors, which represent the overall stream conditions. In some reaches, however, the erosion and cumulative impact from the other factors observed resulted in a lower ranking regardless of the habitat score. For example, stream reach had a relatively good overall habitat score (120.0 and inverse of 80.0), but because of the sedimentation and erosion from side ditches (storm drainage) and intermittent channels, the overall ranking was worse than in several other reaches with better habitat assessment scores. Another example, CC-03, had at least one sanitary sewer line with undermined support structures at risk of leaking. If a leak were to occur, the biotic integrity of the stream would be severely impaired. Again, this severe infrastructure problem increased the rank of this reach by adding 20 points to the score, which put it out of sequence with the habitat score alone. Streams with the lowest overall ratings (highest total scores) have the least potential to support a diverse biological community, primarily due to erosion and sedimentation. ATL\P:\162663\FINAL REPORT DOCUMENTS\FINAL\MASTERPLANREPORT_SECT 3.DOC 3-11

12 TR5-01 Spalding Drive CC-01 TR7-01 TR4-02 TR TR5-03 TR5-02 TR4-01 CC-02 TR1-01 TR1-02 TR TR CC-03 TR2-00 TR2-01 TR TR TR TR TR TR TR CC-04 TR CC-05 TR6-01 TR Stream Segment Breaks Streams Underground Conduit Crooked Creek Watershed Water Bodies Parcels CC = Crooked Creek TR = Tributary T:\Heather\gwinnett\dpudata\APRS\reportfigures3.apr; nmoudry; 10/03/02 N Feet Figure 3 Stream Survey Segments Crooked Creek Storm Water Master Plan Gwinnett County DPU

13 Floodprone = 2 x Bankfull Height Bankfull Bankfull Indicator: change in bank slope, change in vegetation composition, top of point bar When the width of the floodprone stage is the same as or only slightly larger than the width of the bankfull stage, the channel is said to be entrenched or incised FIGURE 4 Bankfull Depth, Bankfull Width, and Floodprone Stage ATL\P:\162663\FINAL REPORT DOCUMENTS\FINAL\MASTERPLANREPORT_SECT 3.DOC 3-13

14 FIGURE 5 Classification Key for Natural Rivers ATL\P:\162663\FINAL REPORT DOCUMENTS\FINAL\MASTERPLANREPORT_SECT 3.DOC 3-14

15 TR B5c TR5-03 TR5-01 G G TR5-02 E5b ND CC-01 E TR TR E5b 88.0 TR G G5c 89.0 G TR7-01 F E TR4-01 CC-02 G5c 94.0 F G TR4-02 G5c 82.0 CC-03 TR1-01 E TR2-00 CC-04 TR1-02 G5c 93.0 G5c 95.0 E6b 83.0 B1 ND G5c TR2-01 B3e 95.0 TR6-01 CC-05 TR G B E E G5 ND G TR TR TR G G5 ND TR G TR B G E TR TR G5 ND E3b Rosgen Stream Type B E F G Stream Segment Breaks Streams Underground Conduit Crooked Creek Watershed Parcels G5c 89.0 Rosgen Level II Stream Classification (see text for description) Habitat Score (see text for description) T:\Heather\gwinnett\dpudata\APRS\reportfigures3.apr; nmoudry; 04/11/03 N Feet Figure 6 Stream Classification and Habitat Scores Crooked Creek Storm Water Master Plan Gwinnett County DPU

16 Spalding Drive TR5-01 CC-01 TR7-01 TR4-02 TR TR5-03 TR5-02 TR4-01 CC-02 TR1-01 TR1-02 TR TR CC-03 TR2-00 TR2-01 TR TR TR TR TR TR TR CC-04 TR CC-05 TR6-01 TR Areas of Active Erosion Stream Segment Breaks Streams Underground Conduit Crooked Creek Watershed Water Bodies Parcels N Feet Figure 7 Erosion Problems Crooked Creek Storm Water Master Plan Gwinnett County DPU T:\Heather\gwinnett\dpudata\APRS\reportfigures3.apr; nmoudry; 10/03/02

17 TR Spalding Drive TR5-01 CC-01 SS TR7-01 S S S TR4-02 S TR TR5-03 TR5-02 TR4-01 CC-02 S S S S S S TR1-01 S TR1-02 S SS S S TR S TR TR S S S S CC-03 TR2-00 S S S S S SS TR2-01 SS S TR S SS S TR TR TR TR TR TR S S S S S CC-04 S S S CC-05 S S S S TR6-01 S Drainage Ditch Problem Score S 1 S 6 Stream Segment Break Streams S 7 Underground Conduit S 8 Crooked Creek Watershed S 9 S 2 S 3 S 4 S 5 Water Bodies Parcels S 10 Score represents relative degradation from influent drainage ditches. T:\Heather\gwinnett\dpudata\APRS\reportfigures3.apr; nmoudry; 10/03/02 N Feet Figure 8 Drainage Ditch Problems Crooked Creek Storm Water Master Plan Gwinnett County DPU

18 TR5-01 Spalding Drive CC-01 TR7-01 TR4-02 S TR TR5-03 TR5-02 TR4-01 CC-02 S SSSS TR1-01 S TR1-02 S TR TR CC-03 TR2-00 S TR2-01 TR TR TR TR S S S TR TR TR CC-04 S TR S S S S S S CC-05 S TR6-01 TR Pipe Problem Score 1 S 6 Stream Segment Break S 2 Streams S S 7 Underground Conduit S 3 S 8 Crooked Creek Watershed S 4 S 9 Water Bodies S 5 S 10 Parcels Score represents relative degradation from storm drain outlets. T:\Heather\gwinnett\dpudata\APRS\reportfigures3.apr; nmoudry; 10/03/02 N Feet Figure 9 Pipe Problems Crooked Creek Storm Water Master Plan Gwinnett County DPU

19 TR5-01 Spalding Drive CC-01 TR7-01 TR4-02 TR TR5-03 S S TR5-02 S S SS TR4-01 CC-02 TR1-01 TR1-02 TR TR TR S S S CC-03 TR2-00 TR2-01 S TR S TR TR S TR TR TR S CC-04 TR CC-05 TR6-01 TR Obstruction Score 1 S 6 Stream Segment Break S 2 Streams S S 7 Underground Conduit S 3 S 8 Crooked Creek Watershed S 4 S 9 Water Bodies S 5 S 10 Parcels Score represents relative degradation from vegetative debris. T:\Heather\gwinnett\dpudata\APRS\reportfigures3.apr; nmoudry; 10/03/02 N Feet Figure 10 Obstructions Crooked Creek Storm Water Master Plan Gwinnett County DPU

20 TR5-01 Spalding Drive CC-01 TR7-01 TR4-02 TR TR5-03 TR5-02 S TR4-01 CC-02 TR1-01 TR1-02 TR TR CC-03 TR2-00 S TR2-01 TR TR TR TR TR TR CC-04 S TR S S TR S S CC-05 TR6-01 TR Dump Site Score S 1 S 6 Stream Segment Break S 2 Streams S 7 S 3 Underground Conduit S 8 S 4 S 9 S 5 Water Bodies S 10 Parcels Score represents relative degradation from litter and trash. Crooked Creek Watershed T:\Heather\gwinnett\dpudata\APRS\reportfigures3.apr; nmoudry; 10/03/02 N Feet Figure 11 Dump Sites Crooked Creek Storm Water Master Plan Gwinnett County DPU

21 Spalding Drive TR5-01 CC-01 TR7-01 TR4-02 TR TR5-03 S TR5-02 TR4-01 CC-02 S TR1-01 TR1-02 TR S TR SS CC-03 TR2-00 TR2-01 TR S S SS S SS TR TR TR S S TR TR TR CC-04 S TR S CC-05 TR6-01 TR Public Utlilty Line Problem Score S 1 S 6 Stream Segment Break S 2 Streams S 7 S 3 Underground Conduit S 8 S 4 Crooked Creek Watershed S 9 S 5 Water Bodies S 10 Parcels Score represents relative degradation near utility (sanitary sewer) lines. T:\Heather\gwinnett\dpudata\APRS\reportfigures3.apr; nmoudry; 10/03/02 N Feet Figure 12 Public Utililty Line Problems Crooked Creek Storm Water Master Plan Gwinnett County DPU

22 TR5-01 Spalding Drive CC-01 S S S TR7-01 S TR4-02 TR TR5-03 TR5-02 S S TR4-01 CC-02 S S S TR1-01 TR1-02 TR TR S S CC-03 TR2-00 TR2-01 TR S S S TR S S TR TR TR TR TR TR S S CC-04 CC-05 S S S TR6-01 TR Road Crossing Problem Score S 1 S 6 Stream Segment Break S 2 Streams S 7 S 3 Underground Conduit S 8 S 4 Crooked Creek Watershed S 9 S 5 Water Bodies S 10 Parcels Score represents relative degradation near road crossings. T:\Heather\gwinnett\dpudata\APRS\crookedfigures.apr N Feet Figure 13 Road Crossing Problems Crooked Creek Storm Water Master Plan Gwinnett County DPU