PLANNING FOR LEVEE BREACH IN DUBUQUE, IA: MODELING & DEVELOPMENT OF MITIGATION STRATEGIES

INTRODUCTION

A LOOK BACK - LEVEE BREACH IN DES MOINES, IOWA, DURING 2008 FLOOD Disasters - Levee Breaches - not expected but result in very severe consequences Major impacts to transportation grid, power grid, communication, property, and public pysche Des Moines River, Des Moines, Iowa 2008 Flood Birdland Levee Breached (USACE 2009 (Kelley, Vroman, Groves, Harder, & Sills ) Temporary flood barrier construction started too late 200 homes, 50 businesses, and North High School were inundated

BACKGROUND AND OBJECTIVES

PROJECT AREA AND GOALS DUBUQUE, IOWA Extend analysis performed by Rock Island District - USACE in 2015 Update HEC-RAS model with up to date version Create breach and response database Add to Mississippi River Conditions Perform parameter sensitivity Define emergency response actions and strategies

MODEL UPDATES

TERRAIN, HYDRAULIC CONTROLS, GRID DEVELOPMENT LIDAR vs Photogrammetry Added Buildings Assumption based on wanting conservative travel times Newer version of HEC-RAS Spatially varying surface roughness (manning s roughness coefficients) Better breakline control

HYDRAULIC RESULTS AND SENSITIVITY

ADDITIONAL MISSISSIPPI RIVER CONDITIONS AND BREACH PARAMETERS Design Final Width Time to Breach

BREACH PARAMETERS Nearly 50 breach scenarios Maximum breach widths were estimated from a study identifying the median (likely) and the 84% confidence level (not as likely, and larger) in similar levee reaches (URS 2013) Similar Levees - 30 ft per hour to 200 ft per hour (Used 100 ft per hour and 200 ft per hour) Not as much guidance for Flood Walls (Used 15 minute to 30 minutes)

BREACH LOCATION 3 200-YEAR EVENT FLOODWALL FAILURE

BREACH LOCATION 1 200-YEAR EVENT MEDIAN BREACH CHARACTERISTICS

BREACH LOCATION 3 200-YEAR EVENT FLOODWALL FAILURE

HARNESSING THE DATA

HARNESSING DATA OVER 50 SIMULATIONS Buildings Transportation Sewers Maximum Travel Travel Time Depth Impacts Time At To 1-ft at On Evacuation To 1-ft at Buildings Evacuation Evacuation Routes Routes Points of Interest

HARNESSING DATA INCREMENTAL INUNDATION EXTENTS FOR OVER 50 SIMULATIONS INITIATION 30 MIN 60 MIN 2 HR

EMERGENCY PLANNING ACTIONS

TEMPORARY FLOOD BARRIERS 7 LOCATIONS IDENTIFIED

AT EACH TEMPORARY BARRIER LOCATION FLOOD DEPTH + ALIGNMENT

AT EACH FLOOD BARRIER LOCATION FLOOD DEPTHS IDENTIFIED

AT EACH FLOOD BARRIER LOCATION QUANTITIES CALCULATED FOR BARRIER LENGTH, FILL, CONSTRUCTION TIME, AND TOTAL CONSTRUCTION HOURS

FLOOD FIGHTING PREPARATION TESTING SCENARIOS Emergency Response effort Mississippi River Forecast - USACE Assume 25.4 ft Forecast Assume a boil or weak area has been identified near upstream end of levee system Near Breach Location 7 Tabbed Flood Binder (+electronic)

FLOOD FIGHTING PREPARATION TESTING SCENARIOS NEAR BREACH 7 Inundation Extents Evacuation Area Transportation Impacts Water Plant

FLOOD FIGHTING PREPARATION TESTING SCENARIOS

CONSTRUCTION OF SHIRAS, FENGLER, FENGER RR CROSS LEVEES DURING 200-YR BREACH 1,500 ft of 4-ft barrier (City already has HESCO) 650 cy of sand 200 hours of labor Reasonable as long as long as planning, stockpiling, and practice occur

SUMMARY

LEVEE BREACH MODELING INTO EMERGENCY PLANNING 2D hydraulic models excellent tool for scenarios (but better learn how to script post-processing) Inundation extents and flood timing can be used by emergency managers in evacuation (reverse 911 and cutting edge alerts) The creation a of comprehensive database compliments emergency flood operations and can inform desktop and practice emergency response exercises The City of Dubuque can now stockpile (and purchase) materials required for and plan for construction time and alignments required to erect life and property saving temporary flood barriers in case of levee weakening during Mississippi River flooding

Percent Decrease in Time to 1-ft Depth RESULTS SENSITIVITY Based on points of interest, moving from 50th percentile to 84 th percentile breach Width and breach time decreased time to 1-ft depth significantly (5 to 50 %) 1 Day Time to 1-ft Depth USACE (Design) 31.5 hr 14 hr 1 hr 4 hr

RESULTS SENSITIVITY PERCENT CHANGE TO 1- FT DEPTH AT US HWY 151

SENSITIVITY RESULTS MAXIMUM DEPTH

SENSITIVITY RESULTS PERCENT CHANGE TO 1-FT DEPTH BY BREACH LOCATION

FLOOD FIGHTING - LOCATIONS

BREACH LOCATIONS Added 2 additional locations

TERRAIN DEVELOPMENT Assumption based on wanting conservative travel times

GRID DEVELOPMENT Newer version of HEC-RAS Better breakline control

POINTS OF INTEREST - BUILDINGS

POINTS OF INTEREST EVACUATION ROUTES

EVACUATION ROUTES MAXIMUM DEPTH

POINTS OF INTEREST MAXIMUM DEPTH

POINTS OF INTEREST TRAVEL TIME

EVACUATION ROUTES TRAVEL TIME

BREACH LOCATION 1 200-YEAR EVENT MEDIAN BREACH CHARACTERISTICS

CONSTRUCTION OF SHIRAS, CROSS LEVEE TO PROTECT WATER PLANT DURING DESIGN EVENT 2,175 ft of 4-ft barrier (City already has HESCO) 965 cy of sand 276 hours of labor May want to consider Permanent barrier