|
|
|
|
|
Friday August 08, 2008 (17:45:58 EST) |
|
|
City Projects
|
|
Upper Reaches of Lower Howard Creek Storm Water
Drainage Study
Study Completed: August 2004
Project Engineer: Allen Patrick Darnell
PURPOSE:
The purpose of this report shall be to perform a preliminary study of the hydraulic conditions in the area of Short Street as requested by the City of Winchester. Our goal shall be to determine the existing physical conditions and structures, which contribute to flooding within the project area. This report shall include preliminary hydraulic calculations in order to identify the problem areas.
This report acknowledges the identified FEMA flood plain areas as shown in Exhibit 2. All state and local regulating authorities prior to construction must approve proposed structures and appurtenances initialized as a result of this report. Once reviewed by the City of Winchester, steps should be taken to perform more detailed studies of significant areas.
Preliminary hydraulic calculations were preformed for the 10 year-24 hour, 25 year-24 hour, 50 year-24 hour, and the 100 year-24 hour storm events.
LOCATION & DESCRIPTION:
The watershed area associated with the study encompasses approximately 215 acres and extends from Main Street west to Fitch Avenue and Sunset Heights. A general overview of the subject watershed and modeled sub watersheds are shown on Exhibit 1. This same area is shown and identified by FEMA on Exhibit 2. Exhibit 3 details the structure located and existing drainage ditches.
In order to perform a preliminary study, hydraulic soil conditions were assumed to be Hydraulic Soil Group "C". Moderate residential coverage was assumed. Time of concentrations was studied for each sub watershed. Each structure was identified in the field and retention volumes taken from GIS maps at a contour interval of five feet. Detailed modeling and volume acquisition was not preformed for this preliminary study.
These watersheds are located in Clark County, Kentucky within the City limits of Winchester. Said watersheds draining to Howard Creek.
CONCLUSIONS:
As this report concluded, the existing drainage structures with the subject watershed hinder the flow of water. This along with the continued restriction of water flow by local residents hinders an already delicate situation. The primary problem seems to be the Hampton Avenue box culvert, which handles the greatest volume of storm flow. Roadway topping did occur in the model for both he Boone Avenue and Hood Avenue culverts also.
The Hampton Avenue box culvert could upsized to handle the necessary flow in order to keep the roadway from topping. However, this would increase the peak storm volume downstream of the culvert by nearly 50 cubic feet per second. As the Flood Study prepared by the Corps of Engineers reports, conditions are near the one-foot marginal elevations of flooding. An increase of 50 cubic feet per second from the Hampton Avenue box culvert would exceed that marginal depth.
Therefore, other storm retention methods should be utilized in order to slow down the peak flows before any of these drainages structures are resized to handle the appropriate storm event. Storm detention basins should be selected carefully so as not to allow peak from proposed basin to add at the crucial times to increase the runoff peak even higher than those experienced under pre-detention conditions. Basins should have sufficient upstream watershed area and volume to make them affective. Detection basins are a maintenance issue. Land values in the residential area also make the construction expensive. All these issues should be weighted closely.
A full copy of this report can be obtained in the Engineering Technicians office City Hall.
Hampton Avenue Drainage Study
Allen Patrick Darnell Engineering presented a preliminary study of the hydraulic conditions in the area of Short Street and Hampton Avenue.
Mr. Darnell stated the following:
Preliminary hydraulic calculations were performed for the 10 year-24 hour, 25 year-24 hour, 50 year-24 hour and the 100 year-24 hour storm events
The watershed area associated with the study encompasses approximately 215 acres and extends from Main Street west to Fitch Avenue and Sunset Heights
The watersheds are located in Clark County, Kentucky, within the city limits of Winchester, with said watersheds draining to Howard Creek
The existing drainage structures with the subject watershed hinder the flow of water, and, along with the continued restriction of water flow by local residents hinders an already delicate situation
The primary problem seems to be the Hampton Avenue box culvert, which handles the greatest volume of storm flow with roadway topping. The Hampton Avenue box culvert could be upsized to handle the necessary flow in order to keep the roadway from topping, but this would increase the peak storm volume downstream of that culvert by nearly 50 cubic feet per second. The Flood Study prepared by the Corps of Engineers reports that conditions downstream of this area are already prone to flooding.
Mr. Darnell recommended that other storm retention methods be utilized in order to slow down the peak flows. Mr. Darnell stated that before any drainage structures are resized to handle the appropriate storm event and storm detention basins, these structures should be selected carefully so as to not allow peak from proposed basins to increase, at the crucial times, the runoff peak even higher than those experienced under pre-detention conditions. Mr. Darnell advised that basins should have sufficient upstream watershed area and volume to make them effective, but detention basins would also become a maintenance issue. Mr. Darnell noted that land values in the residential area would also make the construction expensive.
Commissioner Cox questioned whether upgrading the box culvert on Hampton could cause significant flooding downstream.
Mr. Darnell advised that flooding could be significant and detailed studies would be needed to determine the downstream effects if the box culvert on Hampton were upgraded.
Mayor Dixon advised that the Board would need to decide whether to proceed with the project and if so the following steps would need to be taken:
1. Approve an engineering study to develop a plan
2. Once there is a plan, the Board would have to determine if the plan would be
implemented
3.If the plan is implemented and in place, the Board would need to revisit the Hampton Avenue drainage issue
|
|
Current Project Announcements:
|
|
No New Announcements to display at the moment.
Please check back often for new information!
|
|
|
